Update docs

Author: Dmitry Kobets

docs/code-quality/c26820.md

@@ -7,7 +7,7 @@ helpviewer_keywords: ["C26820"]
 ---
 # C26820
 
-> Assigning by value when a const-reference would suffice, use const T& instead (p.9).
+> Assigning by value when a const-reference would suffice, use const auto& instead (p.9).
 
 For more information, see [P.9: Don't waste time or space](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#p9-dont-waste-time-or-space) in the C++ Core Guidelines.